Hi everyone,
I'm trying to teach myself calculus and have come across this problem.
I have a function of x
f(x) = x^3 + 5x^2 - 8x - 12
so I set this to zero by
f'(x) = 3x^2 + 10x - 8 = 0
then the book I'm using says that I can find the local values of x for min and max and these should be x1 = 0.667 and x2 = -4.000 but it doesn't say how these figures are reached.
Could someone guide me in the right direction please.
Thanks in advance
Andy
When you have a quadratic equation of the form
The "x" solutions are simple to see if you can write your sum of 3 terms as a product by factoring to
We take the factors of -8 that sum to 10 when multiplying out the brackets.
This is (3)4+1(-2) and so
Since 0(anything)=0
then those factors are giving you the 2 solutions
Alternatively,
for
Thanks for the quick reply, it has been a great help. However the answers in the book are 0.667 and -4.000 but I end up with -1.33 and -2.
I'm either losing the plot entirely or having finger trouble, could someone possible check my maths please.